COMMON INITIAL DOSING REGIMENS

• For off-label use in men, the initial dose is typically 0.5–1 mg orally once or twice weekly. The dose is adjusted based on serum estradiol levels and clinical response. It is important to avoid excessive suppression of estradiol, which can lead to joint pain, decreased bone density, and fatigue.

MECHANISM OF ACTION

• Anastrozole is a nonsteroidal aromatase inhibitor. It works by inhibiting the aromatase enzyme, which converts androgens like testosterone into estrogens (e.g., estradiol). This action reduces circulating estrogen levels in the body, balancing the androgen-to-estrogen ratio in men undergoing testosterone therapy.

COMMON SIDE EFFECTS

• Endocrine: Excessive suppression of estradiol may result in joint pain, hot flashes, and decreased libido. Prolonged low estrogen levels can contribute to reduced bone mineral density and an increased risk of osteoporosis.

• Musculoskeletal: Myalgia, arthralgia, and occasional stiffness in joints.

• General: Fatigue, headache, and nausea are reported but are less common in men compared to women undergoing cancer treatment.

• Metabolic: Alterations in lipid profiles, including increased LDL cholesterol levels.

CONTRAINDICATIONS

• Absolute: Known hypersensitivity to anastrozole or any excipients.

• Relative: Osteopenia or osteoporosis, as reducing estradiol excessively can accelerate bone loss. Use with caution in patients with a history of fractures or significant joint pain.

MORE INFORMATION

• FDA Safety Data Sheet can be found here

• Yang Y. The efficacy of anastrozole in subfertile men with and without abnormal testosterone to estradiol ratios. Transl Androl Urol. 2022 [PubMed Link]

• Glaser RL. Subcutaneous Testosterone Anastrozole Therapy in Men: Rationale, Dosing, and Levels on Therapy. Int J Pharm Compd. 2019 [PubMed Link]